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1. Field of the Invention
The present invention generally relates to mechanical joints that connect two pipe ends together. More particularly, the invention relates to threaded rings used to temporarily hold two or more components of any assembly together and then strip away once the components are tightened. Still more particularly, the invention relates to threaded rings used to temporally hold two or more flanges together and then strip away once the pipe ends are tightened.
2. Background of the Invention
In pipeline operations it is often necessary to connect two sections of pipe together that may be at an angle to one another. Pipes that are misaligned are connected together using a joint often referred to as a xe2x80x9cmisalignment jointxe2x80x9d or xe2x80x9cmisalignment coupling.xe2x80x9d A conventional misalignment coupling includes a ball welded or otherwise attached to the end of one of the misaligned pipes and a corresponding socket flange attached to the end of the other pipe. The ball, and the pipe to which the ball connects, is able to rotate and swivel with respect to the socket flange. Both the ball and the socket have bores through their longitudinal axis so that fluid can flow from one pipe through the coupling and into the other pipe. For obvious reasons, such a coupling is also referred to as a xe2x80x9cball joint.xe2x80x9d This type of joint may also be termed a xe2x80x9cswivel coupling.xe2x80x9d The preferred embodiments of the present invention described below represent a substantial improvement to this type of joint regardless of name.
For underwater piping applications, misalignment couplings are used extensively as a result of the elevated costs and difficulties associated with the alignment and assembly of pipe sections under the surface of the sea. The use of misalignment couplings allows sections of pipe that are assembled underwater to have a slackened alignment tolerance with respect to one another.
To assemble underwater piping, specialized and expensive equipment and highly trained divers are utilized. Because of the expenses involved and the limited amount of time that the divers can remain underwater, it is important for sub-sea piping operations to be as fast and simple as possible. One way for valuable underwater time and costs to be saved would be to have misalignment couplings, or ball joints assembled on the surface and sent with the diver underwater as an assembled unit rather than have the diver assemble the components in the water. Assembly on the surface would minimize dive time and its associated expense.
U.S. Pat. No. 4,381,871 discloses one type of a ball joint that can be pre-assembled at the surface. As shown in FIG. 1, which depicts one embodiment of the joint from the patent, the joint connects pipe 12 to pipe 14 and includes a ball and socket swivel system 10 bolted to a standard flange 16. Swivel system 10 includes a ball portion 18, a socket flange 20 and a retaining flange 22. Ball portion 18 is welded to the end of pipe 12 and held in place against socket flange 20 by retainer flange 22. Standard flange 16 is welded to the end of pipe 14. Seal components 24, 26 and 28 help to prevent fluid flowing through the joint from leaking out.
Two separate sets of screws or threaded studs are used to assemble and install the prior art joint of FIG. 1. A short set of screws 30 (although not shown in the cutaway view of FIG. 1, there are multiple screws 30) is used to connect socket and retainer flanges 20 and 22 together. Short screws 30 are used simply to hold the ball 18, socket 20, and retainer 22 components together with seal members 24, 26, and 28 thereby permitting the ball and socket assembly to be pre-assembled. A longer set of threaded studs 32 and corresponding nuts 34 are used to secure the pre-assembled ball and socket swivel system 10 to flange 16. Accordingly, as an assembly, ball and socket system 10 can be lowered into the ocean and the ball portion 18 can be rotated and swiveled by the diver into the orientation that is necessary to connect the pipe 12 to pipe 14. Once the orientation of the ball 18 is determined by the diver, the swivel system 10 is locked and secured to flange 16 by tightening studs 32 and nuts 34.
Although the joint shown in FIG. 1 may be satisfactory, there is considerable room and need for improvement. For instance, it is generally desirable to lower the complexity of a device which usually will reduce the burden on the manufacturing process, minimize the potential for errors to occur, and lower the manufacturing cost of the device. The joint shown in FIG. 1 is a fairly complex type of joint. For instance, the joint requires two sets of studs or screws, 32 and 30, and accordingly, two sets of holes to be drilled through flanges 20 and 22. One set of holes receives long studs 32 while the other set receives short screws 30. Anything that will result in a simpler, easier to manufacture joint would thus be highly desirable.
Accordingly, a ball joint is needed that addresses these concerns. Such a joint preferably would be simpler than conventional joints and could be manufactured at a lower cost. Despite the advantages such a joint would provide, to date no such joint is known to exist.
The issues noted above are addressed in large part by a swivel coupling that includes a ball, a socket flange, a retainer flange, one set of threaded studs and threaded retaining rings threaded about the studs. The threaded retaining rings function to maintain the ball between the socket and retainer flanges at least until the coupling is installed. The threaded retaining rings advantageously permit a second set of screws necessary in prior art joints and associated bores to be eliminated, reducing manufacturing costs and time.
A first embodiment of the threaded retaining ring includes a single piece construction made from a material that has a yield and shear strength lower than that of the threaded studs to which they are threaded. During final assembly in which the pre-assembled swivel coupling is bolted to a standard flange by tightening nuts on either end of the threaded studs, the threaded rings strip out and remain in the assembly without obstructing the function of the coupling. The threaded rings strip away at a load caused by the tightened nuts that is lower than the load on the threaded studs at final assembly. The material specifications and dimensions of the threaded rings can be adjusted to allow any specified amount of flange pre-load required for any given application.
An alternative embodiment of the threaded retaining rings includes a two-piece threaded ring having distinct inner threaded and hardened outer portions. The materials of the two piece construction preferably are selected so that once the inner threaded region strips, the outer portion can be used as a standard washer.